async function async1() {
  console.log('async1 start')
  await async2()
  console.log('async1 end')
}
async function async2() {
  console.log('async2')
}
console.log('scriptstart ')
setTimeout(function() {
  console.log('setTimeout')
}, 0) 
async1()
new Promise(function (resolve) {
  console.log('promise1')
  resolve()
}).then(function () {
  console.log('promise2')
})
console.log('script end')

// scriptstart
// async1 start
// async2
// promise1
// script end
// async1 end
// promise2
// setTimeout

Array.from(new Set(arr.flat(Infinity))).sort((a,b)=> a-b)
